Interferon-alphas are members of the diverse helical-bundle superfamily of cytokine genes (Sprang, S. R. et al. (1993) Curr. Opin. Struct. Biol. 3:815-827). The human interferon-alphas are encoded by a family of over 20 tandemly duplicated nonallelic genes and psuedogenes that share 85-98% sequence identity at the amino acid level (Henco, K. et al. (1985) J. Mol. Biol. 185:227-260). Genes which express active interferon-alpha proteins have been grouped into 13 families according to genetic loci. Known expressed human interferon-alpha proteins and their allelic variations are tabulated in Allen G. and Diaz M. O. (1996) J. Interferon and Cytokine Res. 16:181-184.
Interferon-alphas have been shown to inhibit various types of cellular proliferation, and are especially useful for the treatment of a variety of cellular proliferation disorders frequently associated with cancer, particularly hematologic malignancies such as leukemias. These proteins have shown antiproliferative activity against multiple myeloma, chronic lymphocytic leukemia, low-grade lymphoma, Kaposi's sarcoma, chronic myelogenous leukemia, renal-cell carcinoma, urinary bladder tumors and ovarian cancers (Bonnem, E. M. et al. (1984) J. Biol. Response Modifiers 3:580; Oldham, R. K. (1985) Hospital Practice 20:71).
Interferon-alphas are also useful against various types of viral infections (Finter, N. B. et al. (1991) Drugs 42(5):749). Interferon-alphas have activity against human papillomavirus infection, Hepatitis B, and Hepatitis C infections (Finter, N. B. et al., 1991, supra; Kashima, H. et al. (1988) Laryngoscope 98:334; Dusheiko, G. M. et al. (1986) J. Hematology 3 (Supple. 2):S199; Davis, G L et al. (1989) N. England J. Med. 321:1501). The role of interferons and interferon receptors in the pathogenesis of certain autoimmune and inflammatory diseases has also been investigated (Benoit, P. et al. (1993) J. Immunol. 150(3):707).
Although these proteins possess therapeutic value in the treatment of a number of diseases, they have not been optimized for use as pharmaceuticals. For example, dose-limiting toxicity, receptor cross-reactivity, and short serum half-lives significantly reduce the clinical utility of many of these cytokines (Dusheiko, G. (1997) Hepatology 26:112S-121S; Vial, T. and Descotes, J. (1994) Drug Experience 10:115-150; Funke, I. et al. (1994) Ann. Hematol. 68:49-52; Schomburg, A. et al. (1993) J. Cancer Res. Clin. Oncol. 119:745-755). Diverse and severe side effect profiles which accompany interferon administration include flu-like symptoms, fatigue, hallucination, fever, hepatic enzyme elevation, and leukopenia (Pontzer, C. H. et al. (1991) Cancer Res. 51:5304; Oldham, 1985, supra).
Hepatitis-C virus (HCV) is a nonhost integrated RNA virus with a very high rate of replication and is therefore associated with a large degree of genetic diversity. At least six genotypes and more than thirty subtypes of HCV RNA have been identified. HCV genotype has been shown to be a predictor of response to IFN-alpha therapy. Patients infected with HCV genotypes 2 and 3 have been found to generally respond well to interferon therapy. Patients infected with genotypes 4, 5 and 6 tend to respond less well. Patients infected with HCV genotype 1 tend to respond very poorly to interferon therapy, with about 50% of Genotype 1 patients classified as “nonresponders” towards IFN-alpha therapy. Genotype 1 is currently the most prevalent form of Hepatitis C, infecting approximately 70% of patients in the US and 50% of patients in Europe. Clearly, there is a pressing need for more effective therapies for HCV infection, particularly of the Genotype 1 variety.
There is genetic and biochemical evidence that Genotype 1 HCV (and other subtypes) actively attenuate the IFN-alpha signaling pathway by inhibiting key IFN responsive proteins such as the dsRNA-activated serine/threonine protein kinase PKR (Katze M. G., et al. (2002) Nat. Rev. Immunol. 2(9):675-687). As a likely consequence of this genetic diversity and active inhibition of the antiviral response, HCV (particularly Genotype 1) has the ability to escape the host's immune surveillance, leading to a high rate of chronic infection. The extensive genetic heterogeneity of HCV has important diagnostic and clinical implications, potentially accounting for variations in clinical course, difficulties in vaccine development, and lack of response to therapy.
The present invention addresses the need for interferon-alpha molecules which exhibit enhanced antiviral and/or immunomodulatory efficacy. The invention provides novel interferon-alpha polypeptides and polypeptide conjugates, nucleic acids encoding the polypeptides, and methods of using such molecules. Such molecules would be of beneficial use in a variety of applications, including, e.g., therapeutic and prophylactic treatments, particularly for viral infections and diseases and conditions associated with viral infections. The present invention fulfills these and other needs.